TWI flies to Marshall aid
Marshall Aerospace, the Cambridge aircraft refitting company, has recently called on TWI to assist with refurbishment of critical wing components. Badly worn titanium alloy flap and slat tracks, from Lockheed Tristar aircraft, have been repaired by TIG welding and high velocity oxyfuel (HVOF) spraying in TWI's Arc Welding Department.The relative scarcity and high cost of replacement parts makes repair a very attractive alternative. However, the tight schedules that Industrial Member Marshall Aerospace is required to operate during a refit demand that these parts have to be stripped from the aircraft and refitted typically within 48 hours.
On the first occasion that TWI undertook this repair, it quickly became clear that finding a suitable TIG welding consumable for this titanium alloy was impossible. It was agreed that consumable could be made by machining samples from a scrapped component, which would also give the best compositional match.
The TIG weld repair was completed manually with ample argon gas shielding. After grinding back carefully to the required dimensions, the bearing surfaces were grit blasted, cleaned and HVOF sprayed with a thin coating of cobalt-tungsten carbide.
The final coating provides a significantly more wear resistant finish than the original titanium alloy.
TWI now regularly helps Marshall Aerospace repair flap and slat tracks - with a turnaround of 24 hours.
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